Vascular disease, including heart attack and stroke, are major causes of death and illness in patients with diabetes. This long term goal of this application is to identify novel strategies to reduce vascular disease in diabetes. The balanced production of reactive nitrogen and oxygen species plays a critical role in the regulation of normal vascular function. Diabetes increases oxidative stress in vascular wall cells leading to reduced nitric oxide (NO) bioavailability and endothelial dysfunction. This proposal explores the novel hypothesis that the ligand-activated transcription factor, peroxisome proliferator-activated receptor gamma (PPARg) controls a program of gene expression in vascular endothelium that regulates the balance between the production of reactive nitrogen and oxygen species and that PPARg stimulation exerts vascular protective effects in vivo by directly stimulating endothelial PPARg to increase NO bioavailability. The PI has demonstrated that direct activation of vascular endothelial cell PPARg with thiazolidinediones increased endothelial cell NO release and reduced superoxide production. Aim 1 will examine mechanisms by which PPARg alters endothelial superoxide metabolism in vitro and in vivo. Preliminary data indicate that PPARg activation decreases the enhanced expression and activity of NADPH oxidase in the vascular wall of diabetic animals and attenuates vascular dysfunction. Aim 2 will define the impact of PPARg activation on post- translational mechanisms regulating eNOS activity in vitro and in vivo. Because PPARg ligands do not increase the expression of endothelial nitric oxide synthase (eNOS), this aim will focus on PPARg-mediated alterations in the post-translational regulation of eNOS activity including eNOS-protein interactions and site- specific eNOS phosphorylation events. Aim 3 will determine basal and thiazolidinedione-stimulated vascular endothelial function in normal and diabetic endothelial-specific PPARg null mice. These innovative studies will clarify the vascular consequences of reduced endothelial PPARg function and permit analysis of specific effects of endothelial PPARg activity in vascular function. This proposal will clarify roles of PPARg in vascular regulation in diabetes and contribute to the development of improved strategies for the prevention and treatment of vascular disease associated with impaired endothelial NO production.